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JCJ 8899 



Bureau of Mines Information Circular/1982 




Evaluation of a Combined Face Ventilation 
System Used With a Remotely Operated 
Mining Machine 

By E. Divers, N. Jayaraman, and J. Custer 




UNITED STATES DEPARTMENT OF THE INTERIOR 



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Information Circular 8899 

Evaluation of a Combined Face Ventilation 
System Used With a Remotely Operated 
Mining Machine 

By E. Divers, N. Jayaraman, and J. Custer 




UNITED STATES DEPARTMENT OF THE INTERIOR 
James G. Watt, Secretary 

BUREAU OF MINES 
Robert C. Norton, Director 



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This publication lias been cataloged as follows: 



Divers, Edward F 

hvaluation of a combined face ventilation system used with a re- 
motely operated mining machine. 

(Information circular / United States Department of the Interior, 
Bureau of Mines ; 8899) , 

Includes bibliographical references. 

Supt. of D<5cs. no.: I 28.27:8899. 

1. Coal-mining machinery —Safety measures. 2. Mine ventilation- 
Equipment and supplies— Testing. 3. 1 racers (Chemistry). 4. Sulphur 
hexaf luoride. I. Jayaraman, Natesa I. 11. Custer, J. III. Title. IV. 
Series: Information circular (United States. Bureau of Mines) ; 8899. 



-TN^Q^ilH- [TN813] 622s [622\334] 82-600277 



I CONTENTS 

f ^ Page 

N^ Abstract 1 

\^Introductlon 2 

Q^ Acknowledgments 2 

v;:^Mlne test site description 3 

Preliminary survey 3 

Respirable dust control evaluation 3 

Gas control effectiveness 4 

Comments 6 

Conclusions 7 

ILLUSTEiATIONS 

1 . SFg removed during box cut at various depths 5 

2 . SFg removed during box cut and slab cut 6 

TABLE 

1 . 8-hr gravimetric sampling results 4 









U 

^ 



EVALUATION OF A COMBINED FACE VENTILATION SYSTEM 
USED WITH A REMOTELY OPERATED MINING MACHINE 

By E, Divers, ^ N, Jayaraman, ^ and J. Custer ^ 



ABSTRACT 

This Bureau of Mines report presents results of an underground evalu- 
ation to determine the respirable dust and gas control effectiveness of 
a combined (push-pull) face ventilation system for coal mines. The 
system utilizes both blowing and exhaust curtain, continuous miners 
equipped with radio remote control, and flight conveyors. Bureau of 
Mines tests showed a 97% reduction in respirable dust concentrations 
from the usual cab position on the continuous miner to the remote con- 
trol operator's position. This allowed the remote control operator to 
be well within, and the usual cab position to exceed. Federal respir- 
able dust standards. Tests utilizing a safe tracer gas, sulfur hexa- 
fluoride (SFg), to determine the face ventilation effectiveness of the 
combined blowing and exhaust system showed that the system also has 
excellent methane dispersion capability. 

Where wide entries permit, this combined face ventilation system and 
use of remote control can be a very effective method for dust and gas 
control. 



^Mining engineer, Pittsburgh Research Center, Bureau of Mines, Pittsburgh, Pa. 
^Manager, Safety and Health, Solar Fuel Co., Somerset, Pa. 



INTRODUCTION 



Various research s 
of Mines have consis 
fective ventilation 
and most cost effect 
moving dust and gas 
operations. There 
ventilation systems 
and combined. 



tudies by the Bureau 
tently shown that ef- 
is still the primary 
ive technique for re- 
from coal mine face 
are three basic face 
: Blowing, exhaust. 



Blowing systems can be very effective 
in sweeping gas from the face. They can 
also increase production by allowing 
deeper cuts. Unfortunately, blowing sys- 
tems usually create severe dust problems 
by allowing the dust created by the con- 
tinuous miner to roll back beyond the 
miner operator. The standard procedure 
for alleviating this problem is to place 
a mechanical dust collector (scrubber) on 
the mining machine. Scrubbers are expen- 
sive and create additional maintenance 
problems, but increased production can 
justify their use. 

Exhaust face ventilation can also offer 
good dust control when the line curtain 
is maintained reasonably close to the 
face. Maintaining this curtain is trou- 
blesome, and severe safety problems re- 
sult for personnel extending curtain be- 
yond permanently supported roof. These 
problems can also limit the depth cut, 
thus lowering production. 

Where conditions permit, combined face 
ventilation systems, using both blowing 
and exhaust curtain, potentially offer 
the best features of each, allowing good 
dust and gas control and deeper cutting. 



Required conditions are wide entries, 

20 ft or more, which allow room for both 

curtains, and reasonably good roof to 
allow deep cuts. 

On most continuous miner sections, the 
dust exposure of the continuous miner 
operator is primarily attributable to the 
cutting action of the machine itself. 
Most of the dust cloud originates at the 
face, and the exposure of the operator 
depends largely on how far this dust 
spreads near the cab where the operator 
sits. Radio and other types of remote 
control units that are now available, and 
which weigh only 5 lb, allow the continu- 
ous miner operator to move farther back 
from the face area than the conventional 
position in the cab, thus reducing expo- 
sure to dust. 

Solar Fuel Co. , a division of Gulf+ 
Western Industries, Inc., is using a com- 
bined face ventilation system with a re- 
motely controlled unit, that appears to 
offer high production with excellent dust 
and gas control. An underground test 
program was arranged by the Bureau of 
Mines to evaluate the effectiveness of 
the combined face ventilation system for 
both respirable dust and gas control, 
with special attention to the effects of 
remote control in the continuous miner 
operator's exposure to dust. Since the 
mine seleceted (Solar #5A mine) did not 
have a significant gas problem. Bureau 
personnel used a safe tracer gas (SFg) 
technique developed by the Bureau3 to 
determine face ventilation effectiveness. 



ACKNOWLEDGMENTS 



The authors would like to thank 
Dr. Fred N. Kissell of the Pittsburgh 
Research Center for initially sug- 
gesting the possible advantages of the 
double brattice systems and further 
technical contributions during the 
progress of the studies. The au- 
thors also appreciate the excellent 



cooperation given by 
Solar Fuel Co. 



all personnel at 



^Vinson, R. P., F, N, Kissell, J, C. 
LaScola, and E. D. Thimons. Face Venti- 
lation Measurement With Sulfur Hexafluo- 
ride (SF5). BuMines RI 8473, 1980, 
16 pp. 




MINE TEST SITE DESCRIPTION 



Solar Fuel operates two drift mines in 
the upper Freeport "E" seam, just north 
of Somerset, Pa. Seam height is approxi- 
mately 42 in. All mines utilize flight 
conveyors and radio remote control with 
Jeffrey 101 continuous miners. Typical 
development is three 20-ft-wide entries 
on 50-ft centers. Face crews normally 
consist of five workers: a remote con- 
trol miner operator, roof bolter operator 
and helper, bridge carrier operator, and 
brattice worker-carrier. Typical shift 
production is 350 tons. 

For the preliminary survey the blowing 
curtain was on the left and just behind 
the continuous miner. Spray water flow 
rate was 15 gpm and 70 psig at the noz- 
zle. The exhaust curtain was on the 
right and extended inby 10 ft past the 
blowing curtain. Primary airflow at the 
end of the exhaust curtain was 4,500 cfm. 



Both curtains were hung from roof bolt 
plates with wood wedges, and no special 
effort was made to eliminate curtain sag 
between roof bolts. Indeed, leakage from 
the blowing to the exhaust side of the 
entry allowed the remote control operator 
to remain in fresh intake air. With deep 
penetration into the entry, about half of 
the air leaked to the exhaust side. Al- 
though the volume of leakage was approxi- 
mately 4,500 cfm, no measurable air move- 
ment was detected between the blowing and 
exhaust curtain. Since the continuous 
miner was cutting into a 14-in rockband, 
large quantities of visible dust were 
generated. This dust cloud seldom rolled 
back beyond the inby end of the exhaust 
curtain, and it was very easy for the re- 
mote control operator to stay out of the 
visible dust and still remain within 
20 ft or so of the miner. 



PRELIMINARY SURVEY 



A preliminary underground survey was 
conducted to determine the best dust and 
gas sampling procedures. During this 
survey, two GCA^ RAM-I dust monitors were 
used to rapidly evaluate short-term dust 
concentrations. Simultaneous 10-sec in- 
terval readings were taken for 7 min at 
two locations: one at the remote control 
operator's position, 10 ft outby the con- 
tinuous miner, and the other immediately 
across the entry behind the exhaust cur- 
tain. Safety conditions would not allow 
readings at the usual cab position on the 



continuous miner. During this survey, 
the operator tended to keep about 10 ft 
from the miner and just outby the left 
fender. Respirable dust concentrations 
at this location were approximately 5% 
of those behind the exhaust curtain. 
During this survey the miner was making a 
10-ft-deep slab cut on the left side in a 
50-ft-deep by 20-ft-wide entry. These 
initial observations and dust readings 
were encouraging, and a more thorough 
dust sampling program was initiated. 



RESPIRABLE DUST CONTROL EVALUATION 



For this respirable dust control evalu- 
ation, 8-hr gravimetric (personal) sam- 
plers, identical to those commonly used 
underground, were used. A cluster of 
three samplers was placed in the immedi- 
ate return to evaluate total dust gener- 
ated at the face. An identical cluster 
of three was placed at the usual cab 

^Reference to specific products does 
not imply endorsement by the Bureau of 
Mines. 



position on the continuous miner, and two 
were connected to the radio control unit. 
Samplers were taken for three consecutive 
daylight shifts. Production including 
rock was 350, 295, and 285 tons, respec- 
tively. During this period, 12 place 
changes were made. The remote control 
operator for these tests was positioned 
between 10 and 20 ft from the continuous 
miner. Subsequent analysis of the gravi- 
metric samples showed a 97% reduc- 
tion (table 1) in respirable dust 



concentrations at the remote position 
compared with the cab position on the 
machine. Note that the 3.21-mg/m^ con- 
centration at the usual cab location is 
not In compliance with Federal regula- 
tions (2 mg/m^). 

TABLE 1. - 8-hr gravimetric sampling 
results: Respirable dust concen- 
tration, mg/m^ 

(Mean values appear in parentheses) 



10/26/81 


10/27/81 


10/28/81 


3-Shift 
average 


CAB POSITION ON MACHINE 


3.27 


2.70 


1.84 




4.12 


3.59 


2.20 




5.62 


3.71 


1.80 




(4.34) 


(3.33) 


(1.95) 


(3.21) 


REMOTE 


0.15 


0.10 


0.08 




.13 


.08 


.09 




(.14) 


(.09) 


(.08) 


(0.11) 


RETURN 


7.06 


3.08 


3.41 




7.15 


3.71 


3.28 






3.41 


3.66 




(7.11) 


(3.40) 


(3.45) 


(4.35) 



NOTE, — Comparing the remote oper- 
ator's position to the cab position 
on the machine, the 3.21:0.11 ratio 
of the means is equivalent to 29.1, 
for a dust reduction of 97%. 

These results are consistent with a 
study conducted by Bituminous Coal Re- 
search, Inc. ,^ which indicates that dust 
samplers ahead of the remote control 
operator were exposed to substantially 
higher dust levels than either the sam- 
pler worn by the operator or samplers 
mounted behind the operator. For exam- 
ple, a sampler located just 3 ft ahead of 
the operator's position on the continuous 

^Kost, J. A., and R. D. Saltsman. 
Evaluation of the Respirable Dust Area 
Sampling Concept as Related to the Conti- 
nuous Miner Operator. Bituminous Coal 
Research, Inc., BCR Rept. L-792, January 
1977, pp. 25-30. 



miner may indicate a concentration up to 
twice that at the operator's position. 
It can therefore be seen that a remote 
control system, that keeps the remote 
control operator farther from the face 
can reduce the operator's dust exposure 
considerably. 

GAS CONTROL EFFECTIVENESS 

Determining the gas dispersion ability 
of coal mine face ventilation systems can 
present problems , especially in mines 
like Solar Fuel's #5A mine, which is non- 
gassy. Fortunately, a simple and effec- 
tive technique^ recently developed by the 
Bureau of Mines was available. With this 
technique a small quantity (25 cm-') of 
SFs tracer gas was released immediately 
behind the continuous miner cutter head. 
Simultaneous lO-cm-' grab samples were 
taken at specific time intervals behind 
the exhaust curtain at location S^ 
(fig. 1) and at the remote control oper- 
ator's position. After gas chromatograph 
analysis of the samples, the percentage 
of SF5 removed with respect to time was 
calculated and plotted. This can be com- 
pared with similar tests from other face 
ventilation systems known also to be 
effective. 

Prior to the tests, ventilating air 
volumes , curtain setbacks , and face con- 
figurations were recorded, and a tee was 
placed in line with one end to the SF5 
syringe and the other to a hand-operated 
tire pump with the handle extended. Then 
the SFe was released through 1/4-in-ID 
polyvinyl chloride tubing connected from 
a position just behind the cutting head 
to a position just outby the right fen- 
der. Following a prearranged signal to 
those taking the grab samples , the total 
volume of 25 cm-' of SF5 was injected, and 
the pump handle was depressed several 
times to insure complete dispersion. For 

^Divers, E. F., J. C. LaScola, and G. 
J. Hundman. New Twin Scrubber Installa- 
tion for Continuous Mining Machines. 
BuMines TPR 112, 1981, 10 pp. 



100 




4,500 cfm 



'°'! 


. 


20' 





/?= SFg release point 
5= Grab sample location 
= Remote operator 



i^ 



9,000 cfm 



T/ ? A 




13' to 
end of — 
exhaust 
brattice 



Leakage 

to 

exhaust side 



Test letters A-D show the approximate 
location of the miner for each SFg test 



0.25 



0.50 



0.75 1.00 

TIME, min 



1.25 



1.50 



1.75 



2.00 



FIGURE L - SF. removed during box cut at various depths indicated by tests A, B, C, and D. 



these tests, six grab samples were taken 
at each location (fig. 1) at 5-sec inter- 
vals, followed by six additional samples 
at longer time intervals. These air sam- 
ples were analyzed for SF5 content and 
used to plot graphs showing SF5 removed 
versus time (fig. 1 and fig. 2). 

The first-cut series of SFs tests were 
conducted with the continuous miner mak- 
ing an 8-ft-deep box cut on the right 
(exhaust) side. Four tests were con- 
ducted and no effort was made to influ- 
ence the remote control operator's stan- 
dard cutting procedures. Water spray 
flow rates were 15 gpm and 70 psig at the 
nozzle. In gassy mines, it is assumed 
that the operator would box-cut on the 
blowing side to better disperse face 
methane emissions. Even with the box cut 
opposite the blowing side, the test 



showed good potential methane dispersion. 
SF5 samples showed a rapid rise and decay 
at the return location behind the exhaust 
curtain approximately 10 ft outby the 
continuous miner. This immediate sharp 
rise and decay is typical of good face 
ventilation. 

The face ventilation measurement con- 
ducted in a previous underground study^ 
showed that with conventional sprays, 
1-ft box cut, a 9.5-ft curtain distance, 
and 3,600 cfm of airflow behind the cur- 
tain, 70% of the SF5 was removed in ap- 
proximately 1 min. In this study, 90% 
of SF5 was removed in 1 min or less under 
all conditions of testing from j4 to F, 
indicating a very high degree of effec- 
tiveness for the double-curtain system. 

'Work cited in footnote 3. 



100 




0.75 1.00 1.25 

TIME, min 



2.00 



FIGURE 2. 



SF^ removed during box cut (test F) and slob cut (test E). See figure 1 for explana- 
tion of 0, It, and S. 



The exact release point for the SFg was 
not recorded for the previous study, but 
favored the offside of the boom, just be- 
hind the sprays. For Solar Fuel's under- 
ground test, release was just behind the 



sprays, atop the boom and about 2 ft from 
the edge of the boom on the exhaust cur- 
tain side. The effects of this differ- 
ence, if any, are not known. 



COMMENTS 



Past experience has shown that the ef- 
fects of many underground coal mine dust 
control techniques can be more clearly 
seen when rockbands are being cut. A 
distinct plume can normally be observed 
entering the exhaust curtain, or the duct 
inlet when scrubbers are used. During 
these tests at Solar Fuel, wide rockbands 
(up to 18 in) were cut. This resulted in 
a plainly visible plume from the auger 
that was immediately drawn into the 



exhaust curtain, when the exhaust curtain 
was maintained reasonably close to the 
face. When the exhaust curtain was not 
close to the face, a visible dust cloud 
created by the auger would drift slowly 
back over the continuous miner, beyond 
the cab position on the machine. With 
remote control, the operator could read- 
ily back away from this dust cloud. As a 
result, the remote control operator was 
normally in clean intake air. This 



backaway position seldom exceeded 20 ft 
from the continuous miner. During these 
tests the miner made 12 place changes. 
The remote control operator stayed in 
clean air in all observed cutting 
positions. 



Experience of dust control personnel at 
the Bureau of Mines shows that coal mine 
dust reductions of this magnitude (97%) 
are rare and can be especially important 
to mines with a reduced standard due to 
silica. 



CONCLUSIONS 



The combined face ventilation and 
remote control system used by Solar Fuel 
offers excellent dust and gas control. 
Bureau of Mines tests showed a 97% reduc- 
tion in 8-hr respirable dust concentra- 
tions when comparing the usual cab posi- 
tion on the continuous miner with the 
remote (radio-controlled) position. 
These tests also showed that an operator 
in the cab position on the continu- 
ous miner would be exposed to dust 



concentrations that exceed Federal regu- 
lations (2 mg/m^), whereas he/she would 
be well within Federal limitation at the 
remote position. Other tests with a safe 
tracer gas, SFg, to determine face venti- 
lation effectiveness for methane disper- 
sion showed that the combined face venti- 
lation system was more effective than 
9.5-ft exhaust brattice at 3,600 cfm of 
primary airflow under the conditions 
tested. 



INT.-BU.OF MIN ES,PGH.,P A. 26443 















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